Light-sensitive silver halide photographic emulsion

ABSTRACT

LIGHT SENSITIVE SILVER HALIDE PHOTOGRAPHIC EMULSIONS ARE SUPERSENSITIZED BY COATING WITH A SUPERSENSITIZER CONSTITUTED BY A COMBINATION OF TWO DIFFERENT OXACARBOCYANINE DYES.

May 25, 1971 SHUI SATQ ETAL LIGHT-SENSITIVE SILVER HALIDE PHOTOGRAPHIC EMULSION Filed Dec. 12, 1968 FIG./

400 5'00 6&0

WAVELENGTH (my) United States Patent Office 3,580,723 Patented May 25, 1971 ABSTRACT OF THE DISCLOSURE Light sensitive silver halide photographic emulsions are supersensitized by coating with a supersensitizer constituted by a combination of two different oxacarbocyanine dyes.

In the supersensitization of a silver halide photographic emulsion, it is required to obtain an increased sensitizing effect without fogging (residual color property) and without adverse interaction with any other photographic additives. In the prior art, however the known combinations of sensitizing dyes which are appropriate for optical sensitization are very few.

It is one object of the invention to provide a light-sensitive silver halide photographic emulsion having high sensitivity without any undesired fogging. Another object of the invention is to provide a green light-sensitive silver halide color-photographic emulsion having adequate spectral sensibility to alford the best image reproduction. Still another object of the invention is to provide a high speed, green light-sensitive photographic emulsion which does not suffer from a decrease of spectral sensitivity due to the diffusion of super-sensitizers and the incorporation of a gelatine coagulant or a magenta color coupler.

In accordance with the invention, all of the above objects are satisfactorily accomplished by using, as supersensitizer, a combination of at least one sensitizing dye of Formula I with at least one sensitizing dye of Formula wherein R R R and R are independently selected from the group consisting of a lower alkyl group, a sulfoalkyl group of a carboxyalkyl group; R and R are a lower alkyl group; X is an anionic group; and n is 1 or 2, provided that at least one of said R R R and R is a sulfoalkyl group. Suitable lower alkyl groups include methyl, ethyl, etc. As sulfoalkyl groups are included 3- sulfopropyl, 4-sulfobutyl, etc. The usability of the aboveindicated combination of two difierent sensitizing dyes as a supersensitizer has not been known previously in the photographic art. One of the characteristics of the invention is that remarkable effects are obtained when either one of the sensitizing dyes used has at least one sulfoalkyl group as either one of R R R and R Typical oxacarbocyanine sensitizing dyes having the above-indicated formulas are the following.

For the Formula I C ompound Number Structural formula C2115 CH1:

=CH J=0H- f cum T on on cmoinso u 2 2 3 CHzCHzCHzCHzSOz =CH-(IJ=CH 1|q CZHSQ N- OH on on so u 2 2 2 3 ivmomonzsos =on---o=cn III C2115 N- c H i 2 5 HzCH2CH2SO3 For the general Formula II Compound Numb er Structural formula yon-0:011

l f/ CH; x f/[j I C3115 02115 The essential requirement to accomplish the present invention is to use at least one sensitizing dye of the Formula I and at least one sensitizing dye of the Formula II in combination. All of the sensitizing dyes of the Formula I and II are known as ortho-type sensitizing dyes. Among these, the sensitizing dye of the Formula I is a green light-sensitive sensitizing dye having spectral sensitivity maximum at a long wavelength region of 550-580 m whereas the sensitizing dye of the Formula II is a green light-sensitive sensitizing dye having spectral sensitivity maximum at a short wavelength region of 530-550 m Because of this, if the sensitizing dye of the Formula I or II is used alone, it is not possible to obtain a green light-sensitive photographic emulsion sensitized over a sufliciently wide wavelength region. According to the present invention, it is possible to impart high green light sensitivity to a photographic emulsion.

When using the combination of the sensitizing oxacarbocyanine dyes of the Formulas I and II according to the present invention, new distinct sensitivity maxima which are not found by the sole use of the individual sensitizing dyes appear, due to the synergistic action of the sensitizing dyes, whereby a high speed green lightsensitive photographic emulsion is obtained.

The distribution of spectral sensitivity maxima of the supersensitized photographic emulsion will be easily controlled by the choice of the types and amounts of individual sensitizing dyes of the Formulas I and II. These sensitizing dyes are dissolved first into a Water-miscible organic solvent such as methanol, ethanol, etc. to give a solution which is then added to a photographic emulsion. Alternatively, two organic solvent solutions may be prepared by individually dissolving the sensitizing dyes which are then added to the photographic emulsion. The addition of the sensitizing dyes to the photographic emulsion may be made at any stage during the preparation of said photographic emulsion. In general, it is preferable to make such addition at a stage after the completion of second ripening. The photographic emulsion to which the sensitizing dyes are to be added may be any type of light-sensitive silver halide photographic emulsions including silver iodobromide, chlorobromide, bromide and chloride emulsions. The amounts of the sensitizing dyes may vary depending on the type of photographic emulsion to which said dyes are added, but they are usually within the range of 1 to 100 mg. as the total of the sensitizing dyes I and II per kilogram of the emulsion, the suitable ratio between I and II being 4:1 to 1:4. However, the above-indicated amounts and ratio are not always critical. Further, the photographic emulsions of the present invention may contain a gold sensitizer, a sulfur sensitizer, a reductive sensitizer or a polyalkyleneoxide sensitizer. Further, it may contain the usual photographic additives such as antifoggant, storage stabilizer, hardener, coating aid, etc. In addition to the sensitizing dyes I and II as defined above, other sensitizing dyes including pseudocyanine, carbocyanine and mercocyanine dyes can be used.

The photographic emulsion of the present invention can be coated on a support in a manner known per se, to thereby give a light-sensitive photographic element. Suitable supports include glass plate, cellulose triacetate or polyester film base, and baryta paper.

The present invention will be explained in detail by way of the following examples.

EXAMPLE 1 A high speed photographic negative emulsion is prepared by subjecting a silver iodobromide emulsion containing mol percent of silver iodide to second ripening using the goldand sulfur-sensitization process. Separately, the sensitizing dyes of the Formulas I and II are prepared as 0.1% methanolic solutions. These two methanolic solutions are added singly or in combination in the below-indicated amounts per kg. of the above-said emulsion. Each of the emulsions is stirred at 40 C. for about minutes to obtain sufficiently stable spectral sensitization and thereafter mixed with the indicated amount of l- (4-phenoxy-3-sulfop'henyD-B-pentadecyl 5 pyrazolone (color coupler). The resulting dispersions are adjusted to pH 6.8. Each of the resultant green light-sensitive emulsions is coated on a film base to have light-sensitive photographic films.

These films are exposed to light according to the 118 method K-76l0 and then treated at C. for 10 minutes with a color developer of the following formulation:

N,N-diethyl-p-phenylenediamine sulfate 2.5 Sodium sulfite (anhydrous) 2.0 Sodium carbonate (monohydrate) 82.0 Potassium bromide 2.0

Water to make up one liter.

The thus treated film samples are treated by stopping, fixing, bleaching, water Washing and then drying. Fog and yellow light sensitivity of the film samples are measured. The results are set forth in Table 1, wherein the sensitivity values are expressed as relative speed to the yellow-light sensitivity, defined as 100, of the emulsion added with the sensitizing dye No. (6) alone.

1 In combination.

As for the respective sample emulsion, spectral sensitivity is measured by means of a grating spectrograph (light source 2848" K.).

FIG. 1 shows the spectral sensitivity curve of the silver iodobromide emulsion used in this Example 1. In FIG. 2, the solid line and the dotted line show the spectral sensitivity curves of the emulsions added with the sensitizing dyes No. (2) and No. (6), respectively. FIG. 3 shows the spectral sensitivity curve of the emulsion according to this invention to which the sensitizing dyes No. (2) and No. (6) are added in combination.

As is obvious from the above Table l and the figures, the light-sensitive photographic emulsion according to this invention is more highly supersensitized and much more improved in spectral sensitivity in comparison with the emulsion added with any one of the sensitizing dyes alone.

EXAMPLE 2 A high speed photographic negative emulsion the same as that used in the Example 1 is prepared. The sensitizing dyes according to the present invention are added in combination to the emulsion in the below-indicated amounts per kg. of the emulsion.

The resulting emulsion is further added with the indicated amount of a coupler prepared by dissolving 1- (2,4,6 trichlorophenyl)-3-[3-(2,4-di-tert. amylphenoxyacetamide) benzamide[-5-pyrazolone in di-n-butyl phthalate and ethyl acetate by heating and dispersing the resulting solution in gelatine solution with sodium alkylbenzenesulfonate. The pH value of the resulting dispersion is adjusted to 6.8. Immediately or after incubation at 40 C. for 3 hours, the green light-sensitive emulsion thus obtained is coated and dried on a film base.

A control sample is prepared by using the combination of the sensitizing dyes disclosed in US. Patent 2,688,545 which is coated and dried under the same condition as above. The sensitizing dyes used have the following formulas:

These films are exposed to light in a similar manner to that in Example 1 and then treated at 21 C. for 10 minutes with a color developer of the following formulation:

N-ethyl-N-fl-methanesulfonamido-ethyl-3-methylamino aniline sulfate2.5 g.

Sodium sulfite (anhydrous)2.0 g.

Benzyl alcohol-38 ml.

Sodium hexametaphosphate2.0 g. Sodium carbonate (monohydrate)50.0 g. Potassium bromide-1.0 g.

Sodium hydroxide0.6 g.

Water to make up one liter.

The thus treated film samples are subsequently subjected to the same treatments elfected in Example 1 after development. The results of measurement on fog and sensitivity are set forth in Table 2, wherein the sensitivity values are expressed as relative speed to the yellow light sensitivity, defined as 100, of the emulsion added with the combination of the control dyes (A) and (B).

A reversal color photographic silver iodobromide emulsion containing 3 mol percent of silver iodide is treated with a gelatine coagulant and then subjected to a second ripening using goldand sulfur-sensitization process. Immediately after the second ripening, the resulting emulsion is divided into three portions. To each of the emulsions, are added the sensitizing dyes of the Formulas I and II in combination as 0.1% methanolic solution in the belowindicated amount per kg. of the emulsion.

After completion of the ripening, each of the resulting emulsion is further added with an optimum amount of a stabilizer and the indicated amount of a magenta color coupler prepared by dissolving l-(4-phenoxyphenyl)-3- heptadecyl-S-pyrazolone in di-n-butyl phthalate and ethyl acetate by heating and dispersing the resulting solution in gelatine solution with sodium alkylbenzenesulfonate. The pH value of the resulting dispersions is adjusted to 6.8. Each of the green light-sensitive reversal colorphotographic emulsion thus obtained is coated and dried on a film base.

Immediately thereafter, or after incubation at 55 C. for 3 days or at 50 C. for 3 days under 80% of relative humidity, these films are exposed to light in a similar manner to that as in the Example 1 and then treated at 20 C. for minutes with a first developer of the following formulation:

Water to make up one liter.

The resulting film samples are then treated by stopping, hardening and water washing in the usual manner and subjected to re-exposure with white light. Treatment with the color developer as used in Example 1 is carried out at C. for 12 minutes. The thus treated films are subjected to stopping, bleaching, fixing and water washing and then dried. Results of measurement of speed and fog (color stain) are set forth in Table 3, wherein the sensitivity values are expressed as relative speed to the yellow light sensitivity, defined as 100, of the emulsion added with control dyes immediately after the preparation of the emulsion.

wherein R R R and R are independently selected from the group consisting of lower alkyl groups, and sulfoalkyl groups having up to four carbon atoms; R and -R are lower alkyl groups; X is an anion and n is 1 or 2, provided that at least one of R R R and R is a sulfoalkyl group.

2. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein said supersensitizer is constituted by a combination of 3,3'-disulfobutyl-9-ethyl- 5,6,5',6-dibenzo-oxacarbocyanine and 3,3'-disulfobutyl- 9-ethyl-S ,5 '-diphenyl-oxacarbocyanine.

3. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein said supersensitizer is constituted by a combination of 3,3-disulfobutyl-9-ethyl- 5,6,5',6-dibenzo-oxacarbocyanine and 3,3-diethyl-9-ethyl-S ,5 '-diphenyl-oxacarbocyanine bromide.

4. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein said sensitizer is constituted by a combination of 3,3-disulfopropyl-9-ethy1-5,6,5',6'-dibenzo oxacarbocyanine and 3,3 diethyl-9-ethyl-5,5',-diphenyl-oxacarbocyanine bromide.

5. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein said supersensitizer is constituted by a combination of 3,3-disulfopropyl-9-ethyl- 5,6,5,6-dibenzo-oxacarbocyanine and 3,3-disulfopropyl- 9-ethyl-5,5'-diphenyl-oxacarbocyanine.

TABLE 4 Incubated at; 0., Incubated at 0.80% relative humidity Amount of 0.1% Fresh for 3 days after for 3 days after the methlanolic the preparation preparation so ution sensitizing Dyes (ml.lkg.emulsion) Relatlv; Fog Relativg Fog Relativ; Fog

spee spee spee 1 In combination.

It is evident from the above Tables 2 and 3, that the GO light-sensitive silver halide photographic emulsion according to the present invention is free from fog and highly sensitive in the presence of a coupler and even under severe conditions.

What is claimed is:

1. A light-sensitive silver halide photographic emulsion which comprises, as a supersensitizer, a combination of at least one sensitizing dye of the Formula I with at least one sensitizing dye of the Formula II,

the light-sensitive silver halide photographic emulsion as claimed in claim 1.

10. A light-sensitive silver halide photographic emulsion as claimed in claim 1 wherein the sulfoalkyl group is 3-sulfopropyl or 4-sulfobuty1.

11. A light-sensitive silver halide photographic emulsion as claimed in claim 1 wherein the lower alkyl group is methyl or ethyl.

12. A light-sensitive silver halide photographic emulsioin as claimed in claim 1 wherein the anion is bromide or io ide.

References Cited UNITED STATES PATENTS 2,422,080 7/1947 Collins et a1 96-104 3,411,916 11/1968 Brooker et al 96-404 WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner US. Cl. X.R. 

